This invention relates to a method for the manufacture of alkylated diphenyl oxides in a convenient continuous flow process.
Alkylated diphenyl oxide (ADPO) can be used as high performance synthetic base stocks or as starting material for high performance detergents. Polyphenyl ethers are known for their high temperature properties as noted in xe2x80x9cLubricants end Related Productsxe2x80x9d, Klamann, Verlag Chemie, 1984, pp. 116-121. These products can be used as high performance lubricant base stocks or can be used as starting material for high performance detergents such as the sulfonated ADPO which has been reported as a class of high performance detergent. The known commercial methods for preparing ADPO use Friedel-Crafts catalysts which are not only hazardous but also expensive, being consumed at stoichiometric rates in the reaction but also require aqueous work-up; the large amounts of catalyst residues also present disposal problems. The use of zeolites such as ultra-stable Y catalysts has been proposed, for example, in U.S. Pat. No. 5,552,071 (Rudnick) where zeolites such as USY and MCM-22 are proposed for batch operation. Batch processes are not, however, suitable for large-scale and continuous production. The USY catalyst as disclosed in U.S. Pat. No. 5,552,071 deactivates quickly and large amount of catalyst is needed to achieve high conversion. This solid catalyst is usually not easily regenerable when used in this type of process and, as a result, has to be disposed as solid waste. There is therefore a need for a continuous process for the production of ADPOs using solid catalyst with long cycle durations in a continuous, fixed bed reactor.
We have now found that the catalysts belong to MCM-22 family of molecular sieves have superior activity and can be used in continuous processes to produce ADPO economically in large scale without generating large volumes of catalyst waste.
According to the present invention we therefore provide a continuous process for the manufacture of ADPO by alkylating a diphenyl compound such as diphenyl ether itself with an olefinic alkylating agent by passing a continuous flow of the ether and the olefin under alkylation conditions over a solid particulate catalyst which comprises a molecular sieve of the MCM-22 family, preferably zeolite MCM-22. The process is flexible. By adjusting feed compositions, ADPO of different compositions and wide range of properties are produced.
The diphenyl ether reactant is reacted with the olefinic alkylating agent in the presence of the solid molecular sieve catalyst in a continuous flow process in which the catalyst is held in a fixed bed with the reactants being passed over it under fluid flow conditions. The reactants may be in the liquid, gas or mixed (liquid/gas) phases with liquid phase operation being preferred. The temperatures for the reaction will typically be at least ambient and normally will range up to about 400xc2x0 C. although 200xc2x0 C. (reactor inlet) represents a useful practical working maximum. Pressure may range from ambient up to any range within the equipment rating although in most cases autogenous pressure may be suitable. Typically pressures will range up to no more than about 3,000 kPa (reactor inlet) to permit the use of conventional low pressure equipment. Space velocity (WHSV) will typically be from about 0.1 to 10, more usually from about 0.2 to 2.0 hrxe2x88x921. The catalyst is maintained in a fixed bed and for this purpose, the catalyst is formulated in the conventional manner into particulate form with a size suitable to maintain an acceptable pressure drop across the fixed bed. The molecular sieve component may be formulated into the finished particulate catalyst with binders or matrix materials such as alumina, silica or silica-alumina as is conventional or may be a self-bound catalyst. Particles may be cylindrical, lobed, hollow cylindrical, or other suitable configurations for maintaining bed pressure drop within limits.
The aromatic compound which is alkylated is a diphenyl ether or sulfide compound, that is a compound containing at least two aromatic rings linked by an oxygen or sulfur bridge. This class of compounds includes diphenyl ether itself, which is a preferred starting material both from the view point of cost as well as from the properties of the final products as well as diphenyl sulfide. It also includes the substituted diphenyl ethers where the substituents may typically be hydrocarbon substituents such as alkyl, aryl, alkaryl, or aralkyl groups but other substituents such as phenolic hydroxyl, mercapto, halo may also be present. The bridging atoms need not be limited to oxygen or sulfur as in the diphenyl oxides and sulfides and phenoxathins but may also include nitrogen as in the phenothiazines.
The alkylating agent is an olefinic alkylating agent, normally a hydrocarbon olefin although substituted olefins may also be used. For superior lubricating properties, the longer chain alkyl groups are preferred in the final product, typically from at least eight carbon atoms and preferably at least 10 carbon atoms in order to confer good lubricating performance and good oil solubility characteristics in paraffinic type lubricant materials. For this purpose, olefins of at least eight carbons are preferred although less than eight carbons such as hexene-1 may be used in a similar way. Olefins such as octene, decene, dodecene, tetradecene, hexadecene and octadecene are therefore preferred since olefins of more than 18 carbon atoms do not confer improved solubility or lubricant performance characteristics while tending to cause a deterioration in low temperature viscometrics. The alpha olefins, conveniently available commercially, typically from the ethylene growth reaction, are preferred since they produce alkyl substituents on the aromatic rings which are linear beyond the point of ring attachment and with only a methyl branch at the point of attachment. Thus, the preferred olefinic alkylating agents for alkylated diphenyl ethers which are to be used as lubricants are octene-1, decene-1, dodecene-1, tetradecene-1, hexadecene-1 and octadecene-1. Longer chain olefins such as the long chain olefins sold commercially as xe2x80x9cGulftenexe2x80x9d ((trademark)) may be used if desired, for example, for the manufacture of intermediates where a long alkyl chain is required.
The ratio between the diphenyl ether and the alkylating agent is typically from 1:10 to 10:1 molar although considerable excesses of either reactant may be tolerated, especially of the olefin. Normally, ratios between 1:5 and 5:1 molar are useful. Depending on the ratio, the degree of alkylation may be varied although for lubricant purposes, monoalkylation has been found to provide superior results, as described in U.S. Pat. No. 5,552,071. Ratios between 1:2 and 2:1 molar will be most commonly used.
The alkylation reaction is carried out in the presence of a particulate catalyst which comprises a molecular sieve of the MCM-22 family, preferably zeolite MCM-22. The MCM-22 family comprises the molecular sieve materials MCM-22, MCM-56 and MCM-49. MCM-22 is described in U.S. Pat. Nos. 4,954,325 and 5,100,534 and 5,103,066; MCM-49 and MCM-56 are described in U.S. Pat. Nos. 5,362,697; 5,453,554; 5,557,024; 5,827,491; 5,362,697 and 5,536,894, to which reference is made for a description of these molecular sieves, their properties and methods for their manufacture.
The MCM-22 family catalyst is a solid, long-lasting, highly productive and regenerable catalyst for producing ADPO class compounds. These type of catalysts has much higher productivity and longer catalyst life time than previous reported USY or other zeolites. They are highly suitable for use in the fixed-bed, continuous operation characteristic of the present manufacturing process.